THE MICROCIRCULATION IN EXPERIMENTAL-HYPERTENSION AND AGING

Objective: The purpose of this manuscript is to review the literature concerning the alterations in the microvasculature in experimental hyp ertension and aging. We also present new unpublished data and results where previous studies have not addressed important questions. Methods : The new studies were performed using a chronic cranial window to all ow multiple observations of the cortical surface vasculature over time . In vivo video, microscopic techniques were used to study long-term c hanges in microvascular caliber (vasomotion). In some studies, a chron ic, in-dwelling aortic catheter allowed chaotic analysis of short-term blood pressure and heart rate variations. Results: In these new studi es we demonstrated a reduction in number of small arteriolar endpoints per cortical surface area in the spontaneously hypertensive rat and i n the old Brown-Norway rat. There was also a reduction in the number o f arteriole-to-arteriole anastomotic connections in the older rat, The se vascular changes in the old rat were revised or prevented by calori c restriction. In the old rat, there was also a reduction in the varia bility of blood pressure, heart rate and microvessel caliber (vasomoti on). Conclusions: These studies suggest that there is an alteration in the morphology of the small arterioles in hypertension and aging, tha t may lead to reduced ability to perfuse cortical tissue. In addition, there appears to be a diminution of overall short-term cardiovascular and microvascular control.